Recently, a spacer prepared from a photosensitive resin composition is employed in order to maintain a constant distance between the upper and lower transparent substrates in liquid crystal cells of a liquid crystal display (LCD). In an LCD, which is an electro-optical device driven by a voltage applied to a liquid crystal material injected into a constant gap between two transparent substrates, it is very critical to maintain the gap between the two substrates to be constant. If the gap between the transparent substrates is not constant, the voltage applied thereto as well as the transmittance of light penetrating this area may vary, resulting in a defect of spatially non-uniform luminance. According to a recent demand for large LCD panels, it is even more critical to maintain a constant gap between two transparent substrates in an LCD.
Such a spacer may be prepared by coating a photosensitive resin composition onto a substrate and exposing the coated substrate to ultraviolet light, etc., using a mask, followed by development thereof. Recently, efforts of using a light shielding material for a spacer have been made; accordingly, various colored photosensitive resin compositions have been actively developed.
Recently, a black column spacer (BCS) in which a column spacer and a black matrix are integrated into a single module using a colored photosensitive resin composition has been aimed to simplify the process steps. The colored photosensitive resin composition used in the production of such a black column spacer is required not only to easily form a step difference but also to satisfy sensitivity and development margin characteristics at the same time. Especially, if a cured film formed from a colored photosensitive resin composition has uneven wrinkles on its surface, it may cause a serious disadvantage that the amount of injected liquid crystals may not be uniform due to a defect in the gap between the upper and lower plates during their assembly or that spots may be generated on the display due to a poor transmission of electric signals.
In order to suppress the generation of wrinkles on the surface of a cured film, therefore, a photosensitive resin composition comprising an acrylic resin as a wrinkle generation inhibitor has been proposed (Korean Patent No. 1291480). In Korean Patent No. 1291480, however, since the acrylic resin thus employed comprises (meth)acrylic acid units in a large amount of 60 to 85 mole %, it is difficult to form a step difference of a pattern for forming a light shielding spacer due to such a high acid value of the acrylic binder.